Characterisation of the blood RNA host response underpinning severity in COVID-19 patients (preprint)

Infection with SARS-CoV-2 has highly variable clinical manifestations, ranging from asymptomatic infection through to life-threatening disease. Host whole blood transcriptomics can offer unique insights into the biological processes underpinning infection and disease, as well as severity. We performed whole blood RNA Sequencing of individuals with varying degrees of COVID-19 severity. We used differential expression analysis and pathway enrichment analysis to explore how the blood transcriptome differs between individuals with mild, moderate, and severe COVID-19, performing pairwise comparisons between groups. Increasing COVID-19 severity was characterised by an abundance of inflammatory immune response genes and pathways, including many related to neutrophils and macrophages, in addition to an upregulation of immunoglobulin genes. Our insights into COVID-19 severity reveal the role of immune dysregulation in the progression to severe disease and highlight the need for further research exploring the interplay between SARS-CoV-2 and the inflammatory immune response.

Discovery and Validation of a 3-Gene Transcriptional Signature to Distinguish COVID-19 and Other Viral Infections from Bacterial Sepsis in Adults; A Case-Control then Observational Cohort Study (preprint)

Background: Emergency hospital admissions for infection often lack microbiological diagnostic certainty. Novel approaches to discriminate likelihood of bacterial and viral infections are required to support antimicrobial prescribing decisions and infection control practice. We sought to derive and validate a blood transcriptional signature to differentiate bacterial infections from viral infections including COVID-19.Methods: Blood RNA sequencing was performed on a discovery cohort of adults attending the Emergency Department with confirmed bacteraemia or viral infection. Differentially expressed host genes were subjected to feature selection to derive the most parsimonious discriminating signature. RT-qPCR validation of the signature was then performed in a prospective cohort of patients presenting with undifferentiated fever and a second case-control cohort of patients with bacteraemia or COVID-19.Findings: A 3-gene transcript signature was derived from the discovery cohort of 56 definite bacterial and 27 viral infection cases. In the validation cohort, the signature differentiated bacterial and viral infections with an area under receiver operating characteristic curve (AUC) of 0.976 (95% CI: 0.919-1.000), sensitivity 97.3% and specificity of 100%. The AUC for C-reactive protein and leucocyte count was 0.833 (95% CI: 0.694-0.944) and 0.938 (95% CI: 0.840-0.986) respectively. In the second validation analysis the signature discriminated 34 SARS-CoV-2 positive COVID-19 from 35 bacterial infections with AUC of 0.953 (95% CI: 0.893-0.992), sensitivity 88.6% and specificity of 94.1%.Interpretation: This novel 3-gene signature discriminates viral infections including COVID-19 from bacterial sepsis in adults, outperforming both leucocyte count and CRP, thus potentially providing significant clinical utility in managing acute presentations with infection.Funding Statement: Work in this study was funded by the NIHR Imperial Biomedical Research Centre, the Medical Research Council, the Wellcome Trust and the European Union FP7 (EC-GA 279185) (EUCLIDS).Declaration of Interests: None of the authors have any relevant interest to declare. Ethics Approval Statement: Ethical approval was obtained to take deferred consent from patients from whom an RNA specimen had been collected (or from next of kin or nominated consultee) (REC references 14/SC/0008 and 19/SC/0116).

Retrospective screening of routine respiratory samples revealed undetected community transmission and missed intervention opportunities for SARS-CoV-2 in the United Kingdom (preprint)

In the early phases of the SARS coronavirus type 2 (SARS-CoV-2) pandemic, testing focused on individuals fitting a strict case definition involving a limited set of symptoms together with an identified epidemiological risk, such as contact with an infected individual or travel to a high-risk area. To assess whether this impaired our ability to detect and control early introductions of the virus into the UK, we PCR-tested archival specimens collected on admission to a large UK teaching hospital who retrospectively were identified as having a clinical presentation compatible with COVID-19. In addition, we screened available archival specimens submitted for respiratory virus diagnosis, and dating back to early January 2020, for the presence of SARS-CoV-2 RNA. Our data provides evidence for widespread community circulation of SARS-CoV2 in early February 2020 and into March that was undetected at the time due to restrictive case definitions informing testing policy. Genome sequence data showed that many of these early cases were infected with a distinct lineage of the virus. Sequences obtained from the first officially recorded case in Nottinghamshire - a traveller returning from Daegu, South Korea - also clustered with these early UK sequences suggesting acquisition of the virus occurred in the UK and not Daegu. Analysis of a larger sample of sequences obtained in the Nottinghamshire area revealed multiple viral introductions, mainly in late February and through March. These data highlight the importance of timely and extensive community testing to prevent future widespread transmission of the virus.